This study is proposed to investigate the mechanisms of responsiveness or unresponsiveness in leprosy. The disease forms a spectrum with tuberculoid patients having strong cell-mediated immune (CMI) responses to Mycobacterium leprae while lepromatous patients are unresponsive perhaps due to antigen specific suppressor cells. Why both patient contacts and tuberculoid patients have positive CMI to M. leprae but only tuberculoid patients manifest clinical disease is unknown. We plan to obtain T4 and T8 lymphocyte clones from tuberculoid and lepromatous skin lesions and lepromin skin tests of patient contacts. These clones will be tested for reactivity to M. leprae specific cloned proteins and glycolipid. Our preliminary data demonstrates the feasibility of the proposed methods as well as demonstrating lepromin induced suppressor T lymphocytes from lepromatous lesions. We plan to investigate further the mechanism of action of suppressor lymphocytes in lepromatous leprosy. These studies will improve our understanding of leprosy and aid in developing skin test reagents and vaccines.